docs: correct name of updated from $app/stores (sveltejs#450)

There was a typo in the tutorial for the `updated` store from `$app/stores`. See https://kit.svelte.dev/docs/modules#$app-stores-updated

Author: eddieantonio

content/tutorial/03-sveltekit/08-stores/01-page-store/README.md

@@ -4,7 +4,7 @@ title: page
 
 As we learned [earlier](writable-stores), Svelte stores are a place to put data that doesn't belong to an individual component.
 
-SvelteKit makes three readonly stores available via the `$app/stores` module — `page`, `navigating` and `updating`. The one you'll use most often is [`page`](https://kit.svelte.dev/docs/types#public-types-page), which provides information about the current page:
+SvelteKit makes three readonly stores available via the `$app/stores` module — `page`, `navigating` and `updated`. The one you'll use most often is [`page`](https://kit.svelte.dev/docs/types#public-types-page), which provides information about the current page:
 
 * `url` — the [URL](https://developer.mozilla.org/en-US/docs/Web/API/URL) of the current page
 * `params` — the current page's [parameters](params)
@@ -33,4 +33,4 @@ As with any other store, you can reference its value in a component by prefixing
 </nav>
 
 <slot />
-```
+```